1. Field of the Invention
The present invention relates to a high voltage power supply apparatus for providing a high-voltage current for use, for example, in a copying apparatus or a printer of electrophotographic system.
2. Related Background Art
The electrophotographic copying apparatus or printer employs a high voltage power supply apparatus for the image forming process. Such a high voltage power supply apparatus is designed so as to lower or terminate the high voltage output upon detecting an abnormal current, in case of an abnormality such as a current leakage in a process unit such as a charger or a photosensitive drum constituting the load of the power supply apparatus.
In such a conventional high voltage power supply apparatus, however, the abnormality is detected only for an instantaneous increase in the output current caused, for example, by a leakage, so that an increase of the output current in the average value (or in the effective value) cannot be detected. For this reason, there is encountered a drawback that such a state of the increased output current on average may continue for a long time and may cause damage in the process unit such as the photosensitive drum, thus deteriorating the quality of the copied or printed image relatively quickly.
An object of the present invention is to provide an image forming apparatus not associated with the above-mentioned drawback.
Another object of the present invention is to provide an image forming apparatus capable of monitoring the abnormality in the output of different frequencies for the same load.
Still another object of the present invention is to provide a high voltage power supply apparatus capable of securely protecting the load to which the high voltage current is supplied.
Other objects and features of the present invention will become apparent from the following description which is to be taken in conjunction with the attached drawings.